The instant invention relates to an apparatus and method for depositing subsurface a continuous length of sheath-enclosed signal-transmitting cable. Specifically, the apparatus and method of the invention provides for the burying of a tension-sensitive material, such as a fiber optic or coaxial cable, in a plastimer sheath which protects the cable from compaction, compression and rodents.
A variety of techniques are known for burying signal-transmitting cable. In most cases, the cable to be buried has already been enclosed in a sheath and the sheath, particularly when it is necessary to prevent damage to the cable by chewing rodents, has been armored with a metal covering. The provision of metal armor about the cable greatly increases the cost of the complete assembly. Additionally, in the case of cables which are tension sensitive, such as fiber optic or coaxial cables, the introduction of the cable into a sheath at a point of manufacture and the subsequent winding of the completed assembly on a supply roll may cause undesirable stress in the cable. Placing a fiber optic or coaxial cable under stress can result in loss of signal carrying ability or outright damage to the cable.
An object of the instant invention is to provide an apparatus for depositing subsurface a continuous length of sheath-enclosed signal-transmitting cable.
Another object of the instant invention is to provide an apparatus for dividing or splitting a sheath and placing loosely a signal-transmitting tension-sensitive cable therein at a job site.
A further object of the instant invention is to provide an apparatus which will place a signal-transmitting cable in a divided sheath and allow burying of the assembly formed thereby underground with the division maintained in the sheath.
Another object of the instant invention is to provide an apparatus which will allow the easy bending of a cable-containing sheath and which will orient a split in the sheath to the outside of a curve during placement of the sheath in a trench.
A further object of the instant invention is to provide an apparatus for inserting a cable in a sheath where the sheath is substantially rodent-resistant.
Still another object of the instant invention is to provide an apparatus for burying a split sheath with the split oriented downwards in a trench.
Another object of the instant invention is to provide an apparatus for enclosing a tension-sensitive cable in a sheath, and subjecting the sheath with the cable loosely received therein to bending without placing the cable under tension.
Still another object of the instant invention is to provide a method of depositing subsurface a continuous length of sheath-enclosed cable wherein the sheath is initially opened, the cable inserted therein and the assembly then buried subsurface with wall of the sheath, about the opening, remaining in a non-joined, closed condition. The non-joined condition accommodates distortion and flattening of the sheath during a bending process as the sheath-enclosed cable assembly is buried.
The apparatus of the instant invention includes a surface traversing mobile frame which, in the preferred embodiment, transports the elements of the invention. Means for dispensing a continuous length of hollow sheath and for dispensing a continuous length of signal-transmitting cable are provided. An assembly table for inserting the cable into the interior of the sheath includes a device for dividing a side of the sheath. Devices for forming a subsurface trench and for training the assembly produced by the assembly table are mounted on the frame.
The method of the invention includes opening the side of a hollow sheath along its length, and directing a cable into the opening to produce an elongate, continuous assembly of sheath having the cable inside of it. The wall of the plastimer sheath is permitted to assume a non-joined, closed condition along the region previously opened. A trench is formed to receive the assembly and the assembly is subjected to bending as it travels into the trench, the non-joined condition of the sheath accommodating distortion and flattening of the sheath during such bending. The sheath is then placed in the trench.
These and others objects and advantages of the instant invention will become more fully apparent as the description which follows is read in conjunction with the drawings.